(1) Field of the Invention
The present invention relates to an apparatus for continuously vulcanizing rubber molding extruded from an extruder which introduces the rubber molding into a heating bath to elevate the temperature of the rubber to a predetermined temperature and accelerates vulcanization by maintaining this temperature.
(2) Background Art
In general, a process of continuously vulcanizing rubber molding includes a process of elevating the temperature of rubber molding extruded from an extruder to a vulcanization temperature and carrying out a vulcanization process while maintaining the temperature. In the latter process, heating sources are used. A heating source includes a hot gas utilized in an electric heater, glass beads, a salt bath, and infrared rays.
The heating sources are arranged at proper intervals in a heating bath through which the rubber molding passes and heat irradiation is carried out on the rubber molding. At this time, utilizing a temperature detection sensor installed on a portion of the heating bath, a temperature within the heating bath is usually maintained at a particular value.
Processes of continuously vulcanizing rubber molding, are exemplified by Japanese Utility Model Registration Application First Publication No. Showa 58-163 226 published on Oct. 31, 1983 and Japanese Patent Application First Publication No. Showa 59-96936 published on Jun. 4, 1984.
However, since external heating sources such as hot gas have been used in such previously proposed apparatus for continuously vulcanizing rubber molding, non-uniform vulcanization may easily occur within the rubber molding. Thus, a problem exists such that deterioration of product characteristics has been brought about.
In more detail, in a case where a product is such that a cross sectional form of the rubber molding extruded from an extruder is large and a particular thickness is maintained, a temperature on a surface area of the rubber is not identical to that in an internal portion of the rubber when heated using the external heating source. In other words, only the temperature on the surface of the formed product becomes high. Consequently, the vulcanization of the rubber becomes non-uniform and the physical characteristics of the product obtained is degraded.
To eliminate such a non-uniformity in the vulcanization, the temperature within the heating source may be maintained at a relatively low temperature so as not to produce heat deterioration of the rubber. In this case the heating operation must be continued for a longer period of time. In such a heating means as described above, heating efficiency from the heating source is low so that a length of the heating bath needs to be elongated. Consequently, the apparatus itself becomes quite large.
Furthermore, since, in a case where the external heating source is used as described above, a responsive characteristic of the temperature on the rubber is slow with respect to the elevating temperature operation of the heating source. Temperature elevation is therefore carried out by e.g., using a microwave path as a heating source, but since hot gas is utilized as a heating source in the heating bath, it is difficult to execute accurate temperature control to maintain the rubber molding at an optimum temperature for vulcanization.